Circuit element



1962 G. DIEMER 3,043,958

CIRCUIT ELEMENT Filed Sept. 12, 1960 XNVENTOR GE SINUS DIE ME R BY M 1% United States Patent O masses CmCUlT ELEMENT Gesinus Diemer, Eindhovcn, Netherlands, assignor to The invention relates to a circuit element comprising a combination of at least one electroluminescent radiating member with at least one photosensitive memlber built up into a structural unit, which members are coupled together optically and/ or electrically.

Circuit elements of such a construction may be used, as is known, as electric amplifier units, the electric input signal being supplied to the electrodes of an electroluminescent member coupled optically to a photoconductive member whose electric conductivity is controlled in accordance with the radiation intensity produced in the radiating member and the electrodes of which consequently form the electric output. In addition, such circuit elements may also be used as radiation intensifiers, in which the input signal of the element is formed by a radiation signal of electromagnetic or corpuscular nature which is supplied to a photoconductive member influencing therein the electric conductivity, this photoconductive member being coupled electrically to an electroluminescent member across which the electric voltage is also controlled by the electric conductivity in the photoconductive member, so that in this electroluminescent member a radiation signal is produced having a radiation intensity dependent on the electric conduction occurring in the photoconductive member. Bistable or oscillating electro-optical systems can be obtained by including in the above application possibilities of this circuit element as electric amplifier or as radiation intensifier an electric and optical feedback coupling respectively between the input and output. As electroluminescent substances are used the normal electroluminescent substances such as zinc sulphide. However, it has also been proposed already to use a so-called p-n-recombination radiation source as electroluminescent member, by which is to be understood here a semi-conductive member having a p-n-junction or transition, the radiation in which is produced by recombination of charge carriers which, when the p-n-transition is operated in the forward direction, is injected in the semi-conductive body in the neighborhood of the p-n-transition. The construction and the use of the above circuit elements are described in an article by R. E. Halsted in the book Solid State Phenomena in Electric Circuits, pages 275-287, published by the Polytechniclnstitute of Brooklyn, New York, 1957.

Since these circuit elements are used inter alia to indicate or intensify a signal or to carry out a switching effect, it is of importance that they react rapidly to changes in the signal intensity. The sensitivity and the amplification factor of these circuit elements being determined also by the photosensitivity of the photoconductive member and being in particular proportional to the w product of the photoconductor used, ,u and arespectively being understood to mean the effective mobility and the efiective recombination lifetime of the free charge carriers, it is desirable to use a photoconductor having a high ,u/r product. I

The photoconductors commonly used for the known circuit elements of this type, such as the sulphides and selenides, for example of cadmium, which in most of the cases have to be used in a form activated for the photoconductivity, on the one hand have a satisfactory high ,wr

product, but on the other hand are the cause, owing to their too long response time, of the known circuit elements of this type being too slow for many applications. By the response time of a photoconductor is normally understood here the time required to convert a change of a radiation signal into the resulting desired effective change of the electric conduction. This response time cannot be made shorter than the recombination life 1-, which for these known photoconductors in an activation condition of high photosensitivity is of the order of l millisecond. In practice, the response time of these photoconductors; however, is additionally prolonged by the action of socalled traps.

One of the objects of the present invention is to supply a particularly suitable circuit element of the above type having a photosensitive member which may have a satisfactorily high value of the sensitivity and a satisfactorily short response time.

In a circuit element comprising a combination of at least one electroluminescent radiation member with at least one photosensitive member built up into a structural unit, which members are coupled together optically and/ or electrically, the photoconductive member according to the invention consists of an A B -compound or a mixed crystal of two or more A B -compounds. By an A B -compound is understood here normally an intermetallic semi-conductor compound of an element (A of the third column of the periodic table with an element (B of the fifth column of the periodic table, particularly such a compound between an element of the group boron, aluminum, gallium, indium on the one hand, with an element of the group nitrogen, phosphorus, arsenic, antimony on the other.

These A B -compounds are extremely suitable for use in the above circuit elements, since, as is known, they have a high mobility of the charge carriers and a short recombination life, as a result of which it is possible, owing to the comparatively high value of the mobility at a satisfactorily short recombination life, to achieve a satisfactorily high value of the ,unproduct, as a result of which for the circuit element a satisfactorily high amplification factor and a satisfactorily short response time is achieved.

According to a further aspect of the invention, the photosensitive member preferably comprises such a compound having a value of the forbidden energy zone or gap between the conduction band and valence band between approximately 1 e.v. and 2.5 e.v., such as, for example, lnP', GaP, GaAs, AlSb, AlAs or mixed crystals of GaAs and GaP, that is to say the compound GaAs P in which 0 x 1. Within this range of the forbidden energy zone, the specific resistance of these semi-conductive compounds in intrinsic or compensated conductivity condition has a satisfactorily high value "already at the normal operating temperatures, as a result of which a high limit sensitivity and, owing to the permissibility of a high electric field strength, also a satisfactorily high amplifica tion factor can be achieved, while in addition the for hidden energy zone is not so large again that a satisfactorily short response time would no longer be achievable in a simple manner owing to too large a chance of the annoying and difiicult to avoid incorporation of deep lying trap levels.

Especially in those cases where an optical coupling between the photosensitive member and electroluminescent radiating member is desirable, the commonly used' measures should naturally be taken, such as a suitable choice of the photosensitive and electroluminescent substance to be used, so that one is also photosensitive for the radiation quantum produced by the electroluminescent substance. Therefore, if desired, the two substances may aeeaese be activated in normal manner by incorporating lattice deviations, such as impurities.

In a particularly suitable form of a circuit element according to the invention, the electroluminescent radiation member also comprises an A B -compound, or a mixed crystal of such compounds, preferably from such a compound having a forbidden energy zone exceeding 1 e.v. in this manner, a circuit element according to the invention is obtained having a simple, particularly suitable construction, in which both the electroluminescent member and the photosensitive member consist of an A B -compound, which is possible, because these A B -compounds are also highly suitable as electroluminescent members which, if desired after suitable activation, can be adapted effectively to the spectral distribution of the photoconductivity in the photosensitive member likewise consisting of an A B -compound. Examples of such particularly suitable electroluminescent compounds are AlAs, GaP, AlP, InP or mixed crystals of GaP and InP, the electroluminescent properties of which are known per se. Also the compound GaN is particularly suitable in this connection. Preferably, the electroluminescent radiating member is used in the form of a p-n-recombination radi 'ation source, for which the A B -compounds are also highly effective owing to their suitability of being doped with activators to por n-conductivity, as a result of which the advantage is also obtained that operation with comparatively low direct voltage is possible The manufacture, doping and activation of A B compounds are described elaborately in the literature and therefore need no further explanation here.

Theinvention will now be described, by way of example, with reference to a schematic drawing and some examples.

FIGURE 1 shows diagrammatically a longitudinal sectional view of a semiconductor device according to the invention and a suitable operating circuit therefor.

As an electroluminescent member may be used, for instance a GaP-crystal 1, in which a p-n junction 2 is provided between the n-type zone 3, containing a donor, like for instance sulphur, in a concentration of about 2X10- atoms per mol Gal, and the p-type zone 4, containing an acceptor, like for instance Zn, in about the same concentration. Such a structure may for instance be obtained by diffusion of Zn in an originally sulphur doped n-type crystal. The p-type and the n-type Zones 3 and 4 have been provided with contacts 5 and 6. This GaP crystal with its contacts attached thereto forms the radiating part of the inventive element, and may be provided on a GaAs crystal plate 7, which is provided with contacts 8 and 9 and thus constitutes the photoconductive member of the element of the invention. The GaAs may be activated additionally, if desired, by incorporating impurities therein. In an operating circuit of this element of the invention as an electric signal amplifier or bistable element, an electric signal source S is connected in series with a suitable bias source E between the contacts 5 and 6, so that the pn junction is biased in the forward direction. The output circuit contains a load resistor R in series with a suitable bias source E between the ohmic contacts 8 and 9. In this way the input signal source S determines the radiation intensity excited by the p-n junction and the radiation intensity controls the resistance between the ohmic contacts 8 and 9 and thus the current in the load circuit.

' The same structure may also be used in a circuit known per se as a radiation intensifier, in which the contacts 5 and 6 of the radiation source are connected in series with the contacts 9and 8 of the photoconductive parts, a bias source biasing the p-n junction in the forward direction being included in this circuit. Now an input radiative signal may be applied to the photoconductive part 7, which alters the resistance between the contacts 8 and 9 and this decreases the electrical resistance in the seriescircuit. In this way the alteration of the photoresistance between contacts 8 and 9 alters the radiation intensity of the p-n radiation source between the contacts 5 and 6. The radiation signal of this latter source constitutes the radiative output of the element of the invention.

It will be evident that optical feedback and electrical feed-back couplings between the twoparts can be used in a way known per se for obtaining bistable electrooptical elements. The radiative coupling between the radiative member and the photoconductive member may for instance be obtained by using a semiconductor member consisting partially of GaP and partially of GaAs one part passing over into the other via a gradual mixed crystal formation between these compounds. In this way reflections at the interface between the members are reduced.

In another embodiment may, for example, be used an electroluminescent radiating member of ZnS activated, for example, with an atomic concentration of 10- copper and 09 10* aluminum atoms per molecule ZnS and provided between an aluminum electrode on the one side and a transparent tinoxide electrode on the other on a glass carrier in the form of a layer of, for example, 50 microns thick with the tin oxide electrode facing the glass carrier. For a construction as radiation intensifier without optical feedback coupling, a photoconductive member, for example of gallium arsenide, may be connected in series on the same carrier beside the electroluminescent layer. If an optical coupling between the two members is desired, this can be realized in a simple manner by provid ing the photoconductive member on the other side of the transparent glass carrier opposite to the electroluminescent layer.

It will be clear that the invention is not restricted to the examples of this specification and that, particularly as far as the construction of the electroluminescent member and the photoconductive member and their effective assembly are concerned, many possibilities are available within the scope of the present invention. For example, it may be desirable in many cases to combine more than one radiation member with more than one photosensitive member. In addition, it may be useful in a certain case to construct the photosensitive member as a barrier layer photo-electric cell instead of as a photoconductor, as a result of which the E.M.F. produced in such a photosensitive member may be used.

What is claimed is:

1. A semiconductor device comprising a first, voltagesensitive, electroluminescent, semiconductive body portion generating radiation integrally united with a second, radiation-responsive, photosensitive, semiconductive body portion, electrical connections to the first and second body portions, and means coupling the body portions together, said second photosensitive body portion consisting essentiallyof a substance selected from the group consisting of A -B compound, and mixed crystals of A -B compounds, where A represents an element selected from the :group consisting of boron, aluminum, gallium and indium, and R represents an element selected from the group consisting of nitrogen, phosphorus, arsenic and antimony.

2. A device as set forth in claim 1 wherein the A -B compound has a forbidden energy gap between about 1 and 2.5 e.v.

3. A device as set forth in claim 2 wherein the first body portion also consists essentially of a substance selected from the group consisting of A -B compound and mixed crystals of A -B compounds.

- 4. A device as set forth in claim 3 wherein the A -B compound of the first body portion has a forbidden energy gap exceeding 1 e.v.

5. A semiconductor device comprising a first, voltagesensitive, electroluminescent, semiconductive body portion generating radiation integrally united and optically coupled with a second, radiation-responsive, photosensitive, semiconductive body portion, a pair of electrical connections to the first and second body portions, and means for applying potentials to both pairs of electrical connections, said first and second b-ody portions each consist ing essentially of a substance selected from the 'group consisting of A -B compound, and mixed crystals of A -B componds, where A represents an element selected from the group consisting of boron, aluminum, gallium and indium, and B represents an element selected from the group consisting of nitrogen, phosphorus, arsenic and antimony.

6. A device as set forth in claim 5 wherein the first body portion contains p and n regions forming a p-n junction and the applied potential is of a polarity biasing the said junction in the forward direction.

7. A semiconductor device comprising a first, voltagesensiti-ve, electroluminescent, semiconductive body portion generating radiation integrally united with a second, radi ation-responsive, photosensitive, semiconductive body portion, a pair of electrical connections to the first and second body portions, and means electrically connecting the body portions in series, said first and second body portions each consisting essentially of a substance selected from the group consisting of Am-B compound, and mixed crystals of A -B compounds, where A repre- 6 sents an element selected from the group consisting of boron, aluminum, gallium and indium, and B represents an element selected from the group consisting of nitrogen, phosphorus, arsenic and antimony.

References Cited in the file of this patent UNITED STATES PATENTS 2,836,766 Halsted May 27, 1958 2,863,056 Pankove Dec. 2, 1958 2,885,564 Marshall May 5, 1959 2,929,923 Lehovec Mar 22, 1960 2,959,681 Noyce Nov. 8, 1960 OTHER REFERENCES Loebner: Proceedings of the I.R.E., vol. 43, No. 12, December 1955, pp. 1897-1906.

Tomlinson: Journal of the British Institute of Radio Engineers, vol. 17, No. 3, March 1957 (pp. 141-154).

Ooblenz: Electronics, vol. 30, N0. 11, Nov. 1, 1957 (pp. 144-149).

The Role of Solid State Phenomena in Electric Circuits, Polytechnic Institute of Brooklyn, distributors: Interscience Publishers, N.Y., 1957, pp. 275-287.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,043,958 July 10, 1962 Gesinus Diemer It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Column 4, line 19, for "09 10 "read 0.9 10

Signed and sealed this 26th day of March 1963,

(SEAL) Atteat:

ESTON G. JOHNSON DAVID L. LADD Attesting Officer Commissioner of Patents 

1. A SEMICONDUCTOR DEVICE COMPRISING A FIRST, VOLTAGESENSITIVE, ELECTROLUMINESCENT, SEMICONDUCTIVE BODY PORTION GENERATING RADIATION INTEGRALLY UNITED WITH A SECOND, RADIATION-RESPONSIVE, SEMICONDUCTIVE BODY PORTION, ELECTRICAL CONNECTIONS TO THE FIRST AND SECOND BODY PORTIONS AND MEANS COUPLING THE BODY PORTIONS TOGETHER SAID SECOND PHOTOSENSTIVE BODY PORTION CONSISTING ESSENTIALLY OF A SUBSTAMCE SELECTED FROM THE GROUP CONSISTING OF A$BV COMPOUND, AND MIXED CRYSTALS OF A$BV COMPOUNDS, WHERE A$ REPRESENTS AN ELEMENT SELECTED FROM THE GROUP CONSISTING OF BOROM, ALUMINUM, GALLIUM AND IDIUM, AND BV REPRESENTS AN ELEMENT SELECTED FROM THE GROUP CONSISTING OF NITROGEN, PHOSPHOROUS, ARSENIC AND ANTIMONY. 